American Standard CH530 manual Base Loading Control Algorithm, 20 100 percent RLA

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General Information

Base Loading Control

Algorithm:

This feature allows an external controller to directly modulate the capacity of the chiller. It is typically used in applications where virtually infinite sources of evaporator load and condenser capacity are available and it is desirable to control the loading of the chiller. Two examples are industrial process applications and cogeneration plants. Industrial process applications might use this feature to impose a specific load on the facility’s elecrical system. Cogeneration plants might use this feature to balance the system’s heating, cooling and electrical generation.

All chiller safeties and adaptive control functions are in full effect when Base Loading control is enabled. If the chiller approaches full current, the evaporator temperature drops too low, or the condenser pressure rises too high, Tracer CH530 Adaptive Control logic limits the loading of the chiller to prevent the chiller from shutting down on a safety limit. These limits may prevent the chiller from reaching the load requested by the Base Loading signal.

Base Loading Control is basically a variation of the current limit algorithm. During base loading, the leaving water control algorithm provides a load command every 5 seconds. The current limit routine may limit the loading when the current is below setpoint. When the current is within the deadband of the setpoint the current limit algorithm holds against this loading command.

If the current exceeds the setpoint, the current limit algorithm unloads. The “Capacity Limited By High Current” message normally displayed while the current limit routine is active is suppressed while base loading.

Base loading can occur via Tracer, External signal, or front panel.

Tracer Base Loading: Current Setpoint Range:

(20 - 100) percent RLA

Requires Tracer and Optional Tracer Communications Module (LLID)

The Tracer commands the chiller to enter the base load mode by sending the base load mode request. If the chiller is not running, it will start regardless of the differential to start (either chilled water or hot water). If the chiller is already running, it will continue to run regardless of the differential to stop (either chilled water or hot water), using the base load control algorithm. While the unit is running in base loading, it will report that status back to the Tracer by setting “Base Load Status = true” in the Tracer Status Byte. When the Tracer removes the base load mode request (sets the bit to 0). The unit will continue to run, using the normal chilled or hot water control algorithm, and will turn off, only when the differential to stop has been satisfied.

External Base Loading: Current Setpoint Range: (20 - 100) percent RLA

The UCP accepts 2 inputs to work with external base loading. The binary input is at 1A18 Terminals J2-1 and J2-2 (Ground) which acts as a switch closure input to enter the base-loading mode. The second

input, an analog input, is at 1A17 terminals J2 – 1 and 3 (Ground) which sets the external base loading setpoint, and can be controlled by either a 2-10Vdc or 4-20ma Signal. At startup the input type is configured. The graphs in Figure 13 show the relationship between input and percent RLA. While in base loading the active current limit setpoint is set to the Tracer or external base load setpoint, providing that the base load setpoint is not equal to 0 (or out of range). If it is out of range, the front panel current limit setpoint is used. During base loading, all limits are enforced with the exception of current limit. The human interface displays the message “Unit is Running Base Loaded”. Hot Gas Bypass is not run during base loading. If base loading and ice making are commanded simultaneously, ice making takes precedence.

An alternative and less radical approach to Base Loading indirectly controls chiller capacity. Artifically load the chiller by setting the chilled water setpoint lower than it is capable of achieving. Then, modify the chiller’s load by adjusting the current limit setpoint. This method provides greater safety and control stability in the operation of the chiller because it has the advantage of leaving the chilled water temperature control logic in effect. The chilled water temperature control logic responds quicker to dramatic system changes, and can limit the chiller loading prior to reaching an Adaptive Control limit point.

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CDHF-SVU01C-EN

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Contents X39640670030CDHF-SVU01C-EN Read these carefully Contents General Information Literature changeAbout this manual Unit NameplateGeneral Information = 560 3 stage 935 2 stage Y = 500 3 stage 835 2 stage Commonly Used Acronyms Control Optional PackagesOverview General Duplex unit components front viewGeneral Duplex unit components 2 stage compressor Cooling Cycle Compressor 1 or 2 2 StagePressure enthalpy curve 3 stage compressor Pressure enthalpy curve 2 stage compressor TechView Chiller Service Tool DynaView Human InterfacePower Up Diagram Software Operation Overview DiagramSoftware States Figure Timeline Text FiguresCDHE/F/G sequence of operation auto to running Staging Second Compressor OnStaging Second Compressor Off Satisfied SetpointCDHF/G sequence of operation lead 1/lag Fixed Sequence Compressor 2 / Compressor CDHE/F/G sequence of operation lead 2 lagSequencing Balanced Starts and Hours CDHF/G sequence of operation equalize starts and hoursSimultaneous Compressor Start/ Stop CDHF/G sequence of operation combined startRestart Inhibit Start to Start Time Setting Restart InhibitRestart Inhibit Free Starts Clear Restart InhibitSurface Temperatures Oil and Refrigerant PumpOil refrigerant pump circuit 1 or Base Loading Control Algorithm 20 100 percent RLAGeneral Information Ice Machine Control Sequence of operation ice making running to ice makingHot Water control Unit Control Panel UCP Control Panel Devices and Unit Mounted DevicesUnit Control Panel UCP Variable water flow through the evaporator User-defined language supportOperator Interface DynaView main processorOperator Interface Chiller Stop Prevention/Inhibit Feature How It WorksTop Level Mode Description System Reset Reference Chiller Operating Mode Circuit Operating ModeMain Screen Main Screen Data Fields TableDiagnostic Screen Back button provides navigation back to the chiller screen Operator Interface Report Menu ReportsReport name System Evaporator Report name Circuit EvaporatorReport name System Condenser Report name Circuit CondenserHistoric Diagnostics Log Report name System Ashrae Chiller LogSetting Tab screens provides a user Header ScreenFeature Settings ChillerSystem Mode Overrides Circuit Mode OverridesDisplay Settings PurgeOperator Interface Operator Interface Operator Interface Operator Interface Operator Interface Interprocessor Communication Inter Processor Communications IPC3IPC3 Definitions Bus Management BindingControl System Components Control panel components layoutControl System Components Control Panel Devices Machine Shutdown Manual Reset MMR Head Relief Request OutputMaximum Capacity Relay Compressor Running RelayRefrigerant Monitor Input 1A17 ExopTrmm TRM4 Tracer Comm 4 interface Cdrp Condenser Refrigerant Pressure OutputEpro Enhanced Protection Temperature based Cdrp Refrigerant Pressure Output Option 1A15Condenser Pressure Output Pressure basedRefrigerant Differential Pressure Indication Output Gbas Generic Building Automation System Percent RLA OutputModule Characteristics External Chilled Water Setpoint EcwsExternal Current Limit Setpoint Wpsr WFC Water Pressure Sensing Option1A8, 1A9, 1A11, 1A12 Quad Relay Output Status 1A13, 1A18, 1A19, 1A20 Dual Binary input module1A14 Communication interface Module Recommended Length to Run external Output signals 1A15, 1A16, 1A17, 1A21 Dual Analog Input/output ModuleAnalog Input Unit mounted devices Control System Components Control System Components Control Sequence of Operation Electrical SequenceUCP and Wye-Delta Starter Control Circuits Delay time 200 msec. Opens 2K1 Control Sequence of Operation Control Sequence Operation Test and start timing sequenceAFD Momentary Power Loss MPL Protection Machine Protection Adaptive ControlCurrent Overload Protection Overload trip time versus percent RLAPhase Loss Protection Current Limit ProtectionReverse Rotation Protection Differential to Start or Stop SoftLoadingMinimum and Maximum Capacity Limit Leaving Water Temperature Cutout Evaporator LimitLow Refrigerant Temperature Cutout Head Relief RelayCutout strategy Condenser Limit Restart Inhibit High Vacuum Lockout Oil Temperature Control Controls Chilled Water Reset CWR Outdoor Air TemperatureMaximum Reset Return WaterValues for start reset types Degrees of ResetConstant Return EquationReset Ratio Outdoor air temperature versus degrees of resetReset function for return CWR Reset Ratio = 50% Return CWR Unit Start-Up Procedures Unit StartupDaily Unit Start-Up Live Electrical Components Toxic HazardsSeasonal Unit Start-Up ModeUnit Shutdown Procedures Unit ShutdownOil Pump Heater Operation Seasonal Unit ShutdownPeriodic Maintenance Daily Maintenance and ChecksMoisture Contamination Record Keeping FormsWeekly Maintenance Normal Chiller Operating CharacteristicsHazardous Voltage w/Capacitors Every 3 MonthsOff-Season Maintenance Annual MaintenanceOil Maintenance Oil Change ProcedureHeater Damage Compressor Oil ChangeOil Filter Replacement Replacing Oil FilterMaintenance Oil Supply System ProblemsOther Maintenance Requirements Hazardous Voltage w/ CapacitorsRotary valve in drain position Front View with Refrigerant PumpContains Refrigerant Refrigerant ChargeRecovery and Recycle Connections Leak TestingCleaning the Condenser Proper Water TreatmentCleaning the Evaporator Control Settings AdjustmentsUnit Corrosion Damage Purge System Unit Preparation103 104 105 106 107 108 109 110 111 112 113 114 115 Trane